You can tell a lot about a candidate just from looking at the shirts about them that other people wear.

Barack Obama inspires such CosmoGirl messages as "Obama girl" and "I've got a crush on Barack Obama" (available both on t-shirt and thong). Mitt Romney's are as businesslike as the candidate himself - "Got Mitt?", "To do - vote for Romney 2008". And Hillary Clinton could wear a different t-shirt about herself until the presidential election and not wear the same thing twice. Her supporters really love her ("Hot for Hillary"), and her detractors really hate her (one of the cleaner messages: "No way in Hell-ary").

The rallies are inescapably red, white and blue. The hopefuls are predictably attired in unremarkable suits and tasteful lapel pins. But the political tee has stretched out.

The campaign t-shirt of old used the same designs that appeared on the officially sanctioned buttons and bumper stickers. Now it comes in all colours and moods in a decidedly more democratic process. Supporters and detractors are creating their own designs by computer and selling them online via their own websites, marketplace sites or eBay. Even the campaigns - for better or worse - are loosening up. Mike Huckabee's site, for example, features a long-sleeve shirt with an image of the Republican pastor holding a guitar that looks swiped from the Stray Cats. The accompanying words: Huckabee Rock!

And in a race swamped with candidates, the political t-shirt is in abundance.

Clever wordplay ("ComMITTed" for Mitt Romney supporters) is a standard, as well as messages that shore up the candidate's image (McCain's "Victory with honor"). Then there's sheer style to grab attention: a "Giuliani for prez" shirt uses Seventies-style green and brown script that harkens back to New York City's Studio 54 heyday.

Negative campaigning seems to touch every election these days and the t-shirt is not exempt. Sartorial sallies range this season from the crass ("Hillary cries like a little b****") to the frankly jingoistic ("Thompson 08 because Giuliani is hard to spell").

As the primary campaign has already shown, the message can be an ever-morphing fixture on the campaign trail. T-shirt makers are quick to capitalise on the latest twists. Mere days after Clinton's teary appearance in New Hampshire, shoppers could snap up a host of t-shirts with lachrymose messages ranging from "Vote for Me or I'll Cry" to "Who's Crying Now Hillary 08".

But what you can tell about the race itself from the sales of candidate t-shirts?

Marc Cowlin, corporate spokesperson for cafepress.com, a marketplace website, says on an election year the majority of the site's sales are political t-shirts. The popularity of the garments, designed and sold by users, have fluctuated with that of the candidates, he says.

When Obama won Iowa, users snapped up designs such as 'Barack my world', then as Clinton won New Hampshire, the website was flooded with requests for designs like 'One day a woman will be president'.

Users can even track the candidates on the company's CafePress Meter, which shows who's winning the t-shirt race. Currently Obama is taking 36 per cent of sales with Huckabee trailing with 21 per cent of sales. Clinton is a close third after a surge in sales at the start of last week. Candidates such as McCain, Giuliani and Edwards are all hovering around the 1-2 per cent mark.

Can t-shirt sales reveal the next president? "I think it's too early to predict the result from our t-shirt graph. But it is easy to see that real world news and events affect sales," Cowlin says.

In the meantime as the candidates' election machines strive to stamp their message on the campaigns, supporters make their own mark on the favourites in return. Witness the "John is my homeboy" t-shirt for the white Republican retired Navy pilot McCain. Also available in Obama, Huckabee, Romney and Rudy, with a "homegirl" version for Hillary.

Times recommends

• How to solve the big style questions
• Aids in Africa: ‘It is the staff who really inspire you’
• Video: How to do Beyonce's 'Single Ladies' dance